Biodiesel Benefits and Considerations
Biodiesel is a domestically produced, clean-burning, renewable substitute for petroleum diesel. Using biodiesel as a vehicle fuel improves public health and the environment, provides safety benefits, and contributes to a resilient transportation system.
Public Health and the Environment
The transportation sector is the largest source of greenhouse gas emissions in the United States. A successful transition to clean transportation will require various vehicle and fuel solutions and must consider life cycle emissions. Engines manufactured in 2010 and later must meet the same emissions standards, whether running on biodiesel, diesel, or any alternative fuel. Selective catalytic reduction (SCR) technology in diesel vehicles, which reduces nitrogen oxide (NOx) emissions to near-zero levels, makes this possible. The criteria air pollutant emissions from engines using diesel fuel are comparable to those from biodiesel blends.
Using biodiesel reduces life cycle emissions because carbon dioxide released from biodiesel combustion is offset by the carbon dioxide absorbed from growing soybeans or other feedstocks used to produce the fuel. Life cycle analysis completed by Argonne National Laboratory (PDF) found that B100 use reduces carbon dioxide emissions by 74% compared with petroleum diesel. The California Air Resources Board (CARB) reported similar values from various sources for its life cycle analysis of biodiesel.
Air quality benefits of biodiesel are roughly commensurate with the amount of biodiesel in the blend. Learn more about biodiesel emissions.
Engine Operation
Biodiesel improves fuel lubricity and raises the cetane number of the fuel. Diesel engines depend on the lubricity of the fuel to keep moving parts from wearing prematurely. One unintended side effect of the federal regulations, which have reduced allowable fuel sulfur to only 15 ppm and lowered aromatics content, has been to reduce the lubricity of petroleum diesel. To address this, the ASTM D975 diesel fuel specification was modified to add a lubricity requirement (a maximum wear scar diameter on the high-frequency reciprocating rig [HFRR] test of 520 microns). Biodiesel can improve the lubricity of diesel fuel, even at very low levels. The amount of biodiesel required depends on the specific properties of the diesel fuel, but 2% biodiesel is almost always sufficient for adequate lubricity.
Before using biodiesel, check your engine original equipment manufacturer (OEM) recommendations to determine the allowable blend for your vehicle (see the Engine Technology Forum’s list of diesel vehicles available in the United States for light-duty vehicles and a fact sheet from Clean Fuels Alliance America for heavy-duty vehicles that are compatible with biodiesel.)
Safety
Biodiesel in its pure, unblended form causes far less damage than petroleum diesel if spilled or released to the environment. It is safer than petroleum diesel because it is less combustible. The flashpoint for biodiesel is higher than 130°C, compared with about 52°C for petroleum diesel. Biodiesel is safe to handle, store, and transport. For additional guidance on handling, storing, and transporting biodiesel, reference the Biodiesel Handling and Use Guide (Sixth Edition).
Energy Resilience and Balance
The transportation sector accounts for approximately 30% of total U.S. energy needs and 70% of U.S. petroleum consumption. Using biodiesel and other alternative fuels and advanced technologies to provide diverse clean transportation options strengthens national energy security by increasing resilience to natural disasters and fuel supply disruptions.
Biodiesel is produced in the United States and used in conventional diesel engines, directly substituting for or extending supplies of traditional petroleum diesel. Soybean biodiesel has a positive energy balance, meaning that soybean biodiesel yields 4.56 units of energy for every unit of fossil energy consumed over its life cycle. (See USDA study for more details.)
